Conventionally, in drive devices of a vehicle which have an internal combustion engine and an electric machine, so-called hybrid drive devices, the internal combustion engine is started with the aid of the electric machine, the necessary power for the electric machine, which is operated as a motor in this case, being drawn from an electric accumulator of the drive device. Since operating an electric accumulator of this type at low temperatures, in particular at temperatures below 0° C., may result in rapid aging of the electric accumulator, it may be provided, as described in Japanese Patent Application No. JP 2003-341448 A, to heat the electric accumulator, so that it rapidly reaches a desired operating temperature or a minimum temperature.